feat: MVP-2 completion - search, quick add, backlinks, guided forms

## Search & Retrieval
- Improved search ranking with scoring (title match, favorites, recency)
- Highlight matches with excerpt extraction
- Fuzzy search with string-similarity
- Unified noteQuery function

## Quick Capture
- Quick Add API (POST /api/notes/quick) with type prefixes
- Quick add parser with tag extraction
- Global Quick Add UI (Ctrl+N shortcut)
- Tag autocomplete in forms

## Note Relations
- Automatic backlinks with sync on create/update/delete
- Backlinks API (GET /api/notes/[id]/backlinks)
- Related notes with scoring and reasons

## Guided Forms
- Type-specific form fields (command, snippet, decision, recipe, procedure, inventory)
- Serialization to/from markdown
- Tag suggestions based on content (GET /api/tags/suggest)

## UX by Type
- Command: Copy button for code blocks
- Snippet: Syntax highlighting with react-syntax-highlighter
- Procedure: Interactive checkboxes

## Quality
- Standardized error handling across all APIs
- Integration tests (28 tests passing)
- Unit tests for search, tags, quick-add

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/app/api/search/route.ts

@@ -1,41 +1,18 @@
-import { NextRequest, NextResponse } from 'next/server'
-import { prisma } from '@/lib/prisma'
+import { NextRequest } from 'next/server'
+import { searchNotes } from '@/lib/search'
+import { createErrorResponse, createSuccessResponse } from '@/lib/errors'
 
 export async function GET(req: NextRequest) {
-  const { searchParams } = new URL(req.url)
-  const q = searchParams.get('q') || ''
-  const type = searchParams.get('type')
-  const tag = searchParams.get('tag')
-  
-  const where: Record<string, unknown> = {}
-  
-  if (q) {
-    where.OR = [
-      { title: { contains: q } },
-      { content: { contains: q } },
-    ]
+  try {
+    const { searchParams } = new URL(req.url)
+    const q = searchParams.get('q') || ''
+    const type = searchParams.get('type') || undefined
+    const tag = searchParams.get('tag') || undefined
+
+    const notes = await searchNotes(q, { type, tag })
+
+    return createSuccessResponse(notes)
+  } catch (error) {
+    return createErrorResponse(error)
   }
-  
-  if (type) {
-    where.type = type
-  }
-  
-  if (tag) {
-    where.tags = {
-      some: {
-        tag: { name: tag },
-      },
-    }
-  }
-  
-  const notes = await prisma.note.findMany({
-    where,
-    include: { tags: { include: { tag: true } } },
-    orderBy: [
-      { isPinned: 'desc' },
-      { updatedAt: 'desc' },
-    ],
-  })
-  
-  return NextResponse.json(notes)
 }